Improvement in screw-taps



M. CQJOHNSON.

SCREW-TAP.

Pate nted March 20, 1877.-

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STATES M. CARLYLE JOHNSON, OF HARTFORD, OONNEOTIOUTJASSIGNOR OF HALF HIS RIGHT TO JOHN R. REYNOLDS, OF SAME PLACE.

IMPROVEMENTIN SCREW-TAPS.

Specification forming part of Letters Patent No. 188,466, dated March 20, 1877; application filed February 16', 1877.

To all whom it may concern 1 Be it known that I, M. CARLYLE JOHN- SON, of Hartford, in the county of Hartford anu State of Connecticut, have invented certain new and useful Improvements in Screw- Taps; and I do hereby declare that the following is a full, clear, and exact description thereof, whereby a person skilled in the art can make and use the same, reference being had to the accompanying drawings, and to the into slots in the customary manner.

My invention consists in the mechanical construction of the several parts, which will be hereinafter described.

In the accompanying drawing, Figure l is aside view of my improved screw-tap. Fig. 2 is an end view of the same, with the interior parts shown by dotted lines. Fig. 3 is a .perspective view of one of the cutters removed from the tool. Fig. 4 is a perspective view of one of the. segmental pieces which hold the cutters in place. l

A is the stock, to which the other parts are attached. It is furnished with a cylindrical portion, B, upon which the cutters rest, and into which the screws for holding the parts in place enter. It has the neck or collar 0, against which the ends of -the cutters abut to give them the proper longitudinal position. At the end D it is formed into a square, by which the tool is turned in the customary manner.

E, &c., are the cutters, which are arranged around the central part B at the desired intervals. Four of these cutters are shown in the drawings; but any other number ordinarily used can be equally well applied.

pering often causes them to bend.

F, &c., are segmental pieces, which are in serted between the cutters E, and act as wedges to hold them in place. The body of .the cutter is made of a dovetailed form, and the sides of the segments are made with the same inclination, so as to bear fairly and evenly against the sides of the cutters. These.

segments are shown as being screwed down to the stock B, and the two side segments are slightly removed from B, so that when,

their screws are turnedin they securely clamp the cutters in place.

In the manufacture of the cutters for the class of taps to which my invention relates, it has been found that after they have been properly formed and cut, the process of tem- Toobviate this difliculty, and to make the cutter sufficie'ntly yielding to allow ofits being pressed evenly down upon the interior stock B, I con- .struct it with grooves or channels e e 0 upon its under side, as shown in Fig. 3 of the drawing. These grooves permit of the bending of the cutters when they are pressed by the inclined sides of the segments; and although they may have been warped in the tempering, they are made to lie flat upon the surface of the interior stock, which brings the cuttingedge into its original position, and straight as it-was before being tempered.

It will be observed that my improved construction is equally applicable to the purposes of a reamer; By omitting the screwthread upon the cutters, and forming them with a simple cutting-edge, the tool becomes a reamer.

I claim- 1. The combination of the cutters E an r'rcn;

the Segments Estranged around a central 3. The channels or grooves e in the cutters stock, B, to which the segments F are attached by means of screws, substantially as in described. herein described.

2. The combination of the collar 0 with the 'cutters E and the segments F, substantially as and for the purpose herein described.

M. OARLY LE JOHNSON.

Witnesses:

THEO. G. ELLIS, WILMOT HORTON.

E, substantially as and for the purpose here- 

